Steam generating plant



Patented May 31, 1938 UNITED STATES PATENT OFFICE STEAM GENERATING PLANT' Application March 6, 1935, Serial No. 9,606 In Switzerland March 9, 1934 3 Claims.

This invention relates to series steam generators in which the working medium is fed as liquid to one end of a tube system and is taken off at the other end as superheated steam, the tube system being appropriately supplied with heat.

In such steam generators as usually constructed, the quality, or condition, of the steam delivered by the generator is controlled by means of regulating devices which regulate the generator heat supply, the supply of feed liquid and the output of steam. For plants of small output, however, such regulating devices occupy considerable space in comparison with the steam generator itself; their operation causes a considerable loss of output.

The regulation of steam generators of this type is greatly simplified if the superheating of the working medium in all conditions of operation is made to commence at one and the same point of the tube system. In fact, it has heretofore been proposed to draw off the liquid working medium at a predetermined point in the tube steam systern by means of a liquid separator, and to convey only the dry saturated steam to the superheating zone, but the separated liquid was either led back to the feed supply of the tube system, or led away out of the range of the steam plant.

In accordance with the present invention, the separated liquid is no longer conducted back to the high pressure steam generator, nor is it led away out of the range of the steam plant, but it is led to a low pressure steam generator working as an accumulator. With this arrangement, devices for regulating the quantity of the high pressure working medi-Lun are not necessary but nevertheless, the flexibility of the steam plant is preserved. By the fact that no working medium is led away out of the range of the steam plant, the supplying of additional working medium to take the place of that conducted out of the steam plant is unnecessary, and consequently the danger of introducing feed liquid which is contaminated with deposit-forming materials is lessened. A saving of energy also results, because the heat of the working medium drawn from the high pressure steam generator is recovered in the low pressure part of the system.

The pressure of the steam delivered by the steam generator can, in certain cases, be regulated according to the amount of heat supplied to the generator, the pressure being higher when the heat supply is large than when the heat supply is reduced.

The quantity of liquid Working medium discharged from the liquid separator may be regulated, in accordance with the invention, by means of a device whose operation depends upon the height of the surface of the liquid within the separator. The take-off pipe from the separator may also be provided with a now-limiting device for limiting the ow of steam therethrough, but, at the maximum operating pressure of the steam generator, permitting liquid to flow through the same at the maximum rate at which liquid working medium is supplied to the steam generator.

The invention will be described in connection with the embodiment thereof shown, by way of example, in the accompanying drawing. In this drawing:

Fig. 1 illustrates diagrammatically a steam plant, or system, according to the invention;

Fig. 2 is a sectional view of a detail. v

Fig. 3 shows a modified construction of one of the elements of Fig. 1, and

Fig. 4 illustrates a further modification of this element.

'Referring now to the accompanying drawing, a high pressure water tube steam generator I produces steam which is used for operating a steam engine 2, the steam exhausted from this engine being conveyed in part to the heating element 20 of a low pressure accumulator 3, and in part liqueed in a condenser 4. The condensate from heating element 200i accumulator 3 and the condensate from the condenser 4 lows to a feed liquid tank 5, from which the feed liquid is drawn off and conveyed back to the steam generator I by means of a feed pump 6.

The steam generator I comprises two tube systems, or coils, 8 and I0 suitably mounted in an appropriate furnace structure to which heat is supplied, as will be described below. These two tube systems are connected in series, and the working medium is fed at a uniform rate, as liquid, to the lower end 1 of tube system 8. The liquid is in part evaporated in tube system 8 and arrives as a mixture of vapor and liquid at the separator 9, where the vapor is separated from the liquid and ows on through tube system I0 which operates as a superheater. The superheated steam is led from the upper end II of superheater I0 through pipe I2 to the high pressure cylinderor stage I3 of the steam engine 2. Manually operated valve I4 is provided in steam line I2 for regulating, if necessary, the quantity of steam flowing to the engine. After expansion in the high pressure stage I3, the steam flows through a pipe I5 to a four-way connection I6, from which, according to the existing pressure conditions, it is conveyed either through pipe I1 and governor valve 2l to the low pressureA cylinder or stage I 3 of engine 2, or through the line I9 to the heating element 29 of the low pressure steam generator 3, as previously mentioned.

A speed governor 22 of the engine 2 actuates governor valve 2I and thereby controls the quantity of steam flowing to the low pressure stage I8 in such a way that on an increase of the engine speed, the flow cross section of governor valve 2l is decreased, and on a reduction of speed, is increased. The steam discharged from loW pressure stage i5 is conveyed through line 23 to condenser 4, in which it is condensed by means of the cooling coil 24 which is appropriately'supplied with cooling water, the amount of steam thus conveyed to condenser 4 depending upon the power output of engine 2. The'condensate is removed from condenser 4 by a pump 25 through line 25, and is conveyed through line 21 to the feed liquid tank 5. The liquid level in this tank can be observed by means of a gauge `23. The portion of steam delivered to four-way connection I6, which is not required by the low pressure stage I8 of engine 2, is condensed in heating element 29 of low pressure generator 3. Thus the amount of heat supplied to low pressure generator 3 in this manner, depends upon the power output of engine 2.

Heating element 29 is submerged in the body of liquid working medium contained within low pressure generator 3 and it will be understood that heat from the working medium within heating element 20 is transferred to this body of liquid, thereby causing ebullition and the generation of steam within the shell of low pressure generator 3. The condensate from heating element 29 is conveyed by means of pipe 29 to the feed liquid tank 5.

The liquid working medium separated in the liquid separator 9 is conveyed through the line 39 to the heating element 20 of low pressure generator 3, the heat contained in this liquid thereby being used for the production of low pressure steam, together with the heat of the vapor entering heating element 20 through line I9. The liquid Working medium from separator 9, after passingthrough heating element 20, is carried, along with the condensate resulting from the liqueication of the vapors from line I9, through line 29 to feed liquid tank 5.

A flow-limiting device 32 is provided in line 39 for limiting the maximum rate of discharge of working medium from separator 9, and so for preventing the discharge of an appreciable quantity of steam through line 30. A manually operated valve 3| is placed in line 30 for the purpose of cutting off the flow of liquid from separator 9, and for the purpose of regulating the rate of flow of this liquid as desired.

The liquid working medium conveyed through line 39 from separator 9 can also be led directly into the shell of low pressure steam generator 3 by means of line 34 which is connected with the lower portion of the shell of generator 3. Valves 33 and 35 are arranged to control the low of the liquid from separator 9 for this purpose. In this way, the liquid from separator 9 is added to the liquid working medium in low pressure generator 3, and the heat contained in the liquid from separator 9 is transferred directly to the body of liquid in generator 3 instead of indirectly by means of the heating element 28.

In the event that the amount of steam consumed in the high pressure stage I3 of engine 2 is less than that produced by steam generator I, the pressure in line I2 will increase, and when a predetermined pressure is reached, a pressure operated valve 31 is opened. This permits the steam to pass from line I2 through line 36 into line 38. From line 38 the steam is conveyed by means of a branch pipe 39 to the four-way connection I6, from which, in case the low pressure stage I8 of engine 2 does not take the steam, it flows into heating element 20. Should the conditions be such that it is impossible for heating element 20 to condense the steam at a suiciently high rate, then the surplus steam passes off through a safety valve 48 to the atmosphere.

In case the steam produced by the steam generator I is temporarily not sufcient to meet the steam requirements of engine 2, the steam plant is so arranged that as soon as the steam pressure from generator I falls, low pressure steam from the generator 3 is immediately made available for operating the engine 2. For this purpose the steam is led from the steam space of generator 3 through a pipe 4I to a pressurecontrolled valve 43 and thence through line 39 to four-way connection I5, pipe I1 and the low pressure stage I8 of engine 2.

Pressure-controlled valve 43 is actuated by means of a piston 42 operating in a cylinder, the upper end of which is connected to pipe 38 so asy to be inuenced by variations in the pressure of steam delivered from generator I through lines I2 and 36 and valve 31. When, therefore, the pressure of the steam produced by generator I falls, the pressure upon the upper side of piston 42 is reduced, thereby allowing spring 44, on the lower side of piston 42, to open valve 43.

If desired, a portion of the steam produced by low pressure generator 3 may be conveyed by means of lines 45 and 45 to other steam-consuming devices (not shown), such, for example, as heating devices or additional steam engines. For regulating the pressure in line 46, there is provided a second pressure-controlled valve 41, the valve member of which is controlled by means of piston 48. In case of a rise in pressure in line 46, piston 49 is forced downwardly thereby, and causes the flow cross section of valve 41 to be decreased, and conversely, upon a fall of pressure in line 4S, spring 49 urges piston 48 and its connected valve member upwardly, thereby increasing the iiow cross section of valve 41.

In order to replace losses of working medium occurring in the high pressure circuit, an auxiliary condenser 58 is provided to which steam is conveyed through pipe 5I from line 45. The condensate from condenser 50 is led through pipe 52 into line 29, and thence to feed liquid tank 5. The feed liquid from tank 5 is delivered to feed pump 6 for generator I by means of pump 55 and line 56.

The make-up liquid working medium for low pressure generator 3, and in fact for the entire system, is drawn from a tank 58 by means of a pump 51 which delivers the make-up liquid through pipe 59 to a feed heater 68 heated by the flue gases of generator I. From this heater, the make-up liquid flows through pipe 8l into the bottom of generator 3.

A safety valve is provided to prevent the pressure within generator 3 from becoming too high. Generator 3 is provided also with a circulating pump 53, connected in a circulation pipe 54 for the purpose of regulating the circulation of liquid working medium within generator 3.

A particular form of now-limiting device 32 for limiting the maximum flow of liquid from separator 9 is shown in Fig. 2. As shown in this gure, the flow-limiting device comprises a nozzle 62, the flow cross section of which is such that at the maximum permissible operating pressure of steam generator I, the nozzle will pass the total quantity of liquid working medium delivered by feed pump 6 to tube system 8. As the rate of ow of this nozzle is proportional approximately to the density of the medium iiowing through it, should steam be discharged through nozzle 62 into pipe 3E, the rate of steam flow would be much less than the rate of liquid flow. Thus, for example, with steam flowing through the nozzle, the weight of steam passing the nozzle in a given time and under a given pressure, would amount only to approximately 116 of the weight of liquid which would .pass through the nozzle n the same time. In this way, an automatic regulation of the quantity of working medium drawn from separator 9 is accomplished.

Steam generator I is supplied with heat by means of a liquid fuel burner 6E to which fuel is supplied by means of a pipe 65 in which is located a hand-operated valve 61. The combustion air is supplied through a conduit 68 in which is placed a hand-operated valve 69.

The operation of the steam producing plant, or system, is as follows:

Liquid working medium is supplied to the steam generator I at a constant, or unvarying, rate by means of feed pump 6, and the output of steam from generator I is regulated by varying the amount of heat supplied to the generator. This regulation is accomplished by manipulating burner valves 61 and 69 in accordance with variations of a working condition of low pressure generator 3, such, for example, as variations in the level of liquid working medium in this generator, which can be observed by means of a gauge B3, or by variations in the pressure of the steam generated by generator 3, which can be observed by means of a steam gauge B4.

A larger or smaller quantity of the liquid working medium in tube system 8 of generator i will be evaporated according to the amount of heat produced by burner 66. The non-evaporated liquid is separated in liquid separator 9 and conducted away by means of pipe 30, as previously described, and employed for supplying at least a portion of the heat required for the operation of low pressure steam generator 3, after which it is re-circulated through tube system 8 of generator I.

The regulation of the temperature of the steam at the discharge end II of tube system I of generator I is automatic. This is because of the fact that with a large supply of heat to generator I, an increased quantity of liquid is evaporated in tube system 8 so that a large amount of heat is required to superheat this large supply of steam owing from separator 9 to superheater I0. Conversely, when the supply of heat to generator I is small, the quantity of steam generated is also small, so that the amount of heat supplied to the generator is still able to superheat this small quantity of steam to the prescribed temperature.

It will be understood that instead of the reciprocating steam engine 2 indicated in the drawing as the prime mover of the power plant, one or more turbines may be employed. Other changes may be made in the system which come within the scope of the appended claims, Without departing from the invention.

The steam plant of the present invention has the advantage that more or less complicated devices heretofore employed for regulating the temperature of this type of steam generator are done away with, and nevertheless the temperature of the steam is maintained substantially constant without the necessity of accommodating within the generator a large volume of liquid working medium, The system of the present invention is particularly advantageous in connection with steam generating plants of small and moderate size, because of the fact that in these sizes, the regulating devices occupy a large amount of space in the steam plant in comparison with the size of the steam generator itself. Moreover, the expense and difculty of maintaining such regulating devices in proper operating condition is avoided.

Instead of providing a throttling device in the discharge line of the separator the height of the water level in the separator may be regulated. As shown in Fig. 3 a float member is provided within the separator. The float member raises a valve stem 82 when the water level 8l rises and increases the cross section for the water discharged from the separator. On the other hand vthe cross section is decreased if the Water level sinks and the position of the valve stem is lowered.

In other cases the separator may be suspended in a yielding manner, for example by a spring 83 and connected by a lever 84 with a valve 85, as shown in Fig, 4. The separator is connected by means of two flexible tubes 86 and 81 with the steam generator and by a further flexible tube 83 with the accumulator. If there is a great quantity of water in the separator, the position of the separator is lower than with a smaller quantity of water. The variation in the height of the seprator indicates the quantity of liquid contained in it, and this variation is made use to alter the cross-section of the valve 85 by means of the lever 84.

I claim:

1. In a steam system adapted to supply power and heat in fluctuating amounts, a high pressure tubular continuous-flow steam generator having a, vaporizing zone and a superheating zone, a pump conveying feed liquid in unvarying amount to the steam generator, a liquid separator connected between the vaporizing and superheating zones of the steam generator, an engine plant having high and low pressure stages, said high pressure stage being connected to receive superheated high pressure steam from the superheating zone of the steam generator, a low pressure steam generator having a steam receiving heating element connected between the low and high pressure stages of the engine plant, and a pipe conveying unevaporated liquid from the liquid separator to the steam receiving heating element of the low pressure steam generator.

2. Apparatus in accordance with claim 1 in which a nozzle is connected in the pipe leading from the liquid separator to the steam receiving heating element of the low pressure generator, said nozzle, at the operating pressure of the steam generator, allowing the total quantity of liquid feed to the high pressure steam generator to pass into said heating element.

3. Apparatus in accordance lwith claim 1 in which a by-pass pipe is provided which during periods of production of excess high pressure steam by the high pressure steam generator, leads said steam into the steam heating element of the low pressure steam generator.

HANS CONRAD EGLOFF. 

